1) They can NOT happen "anywhere" they can only occur if you are dynamically building SQL Statements.
Therefore
a) The code you quoted CAN NOT have a SQL Injection Attach Exposure.
b) An application using exclusively stored procedures also CAN NOT BE WRITTEN such that the APPLICATION exposes the database to SQL Injection. [This does NOT preclude errors on the part of the DBA writing the stored procedures, but that is not done in the context of the Application or even (in 99.99% of the cases) in managed code of any language.

